The Truth About Keto
What the top research says about ketone supplements.
Post summary
Ketone supplements are having a moment, with top ultrarunners saying they boost performance.
This comes on the heels of the ketogenic diet, which some say is ideal for weight loss, fixing brain fog, reducing anxiety, and more.
We spoke with leading ketone researcher and expert Dominic D’Agostino to cut through the noise surrounding the fitness industry’s hot new supplement.
You’ll learn whether ketone supplements are worth it for your goals.
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The post
A quick note from Michael: I’m slowly bringing smart new voices into Two Percent. By that I mean skilled journalists who live interesting lives, understand science, and speak with experts often. This will infuse Two Percent with new reporting and ways of thinking and seeing the world.
Today’s post is by Emily Pennington. Emily is a writer, adventurer, and the author of Feral: Losing Myself and Finding My Way in America’s National Parks. She’s written for the New York Times, Wall Street Journal, and Outside. Her last Two Percent post was about how she lost and found sleep (seriously, her sleep was a mess!).
I recently noticed a lot of online chatter about how ketone supplements can improve fitness. So I asked Emily to delve into the science, speak to top researchers, and see if there’s any truth to the claims.
Here’s Emily …
The performance promise
In late 2024, trail runner David Roche smashed the fastest known time at the grueling Leadville 100-mile ultrarun. His not-so-secret weapon: Ketone supplements.
For years, Roche dismissed ketone supplements as expensive hype. Then he read a small 2023 study1.
The researchers subjected nine cyclists to two trials of brutal workouts. During the first trial, they finished their workout with a carb recovery drink. During the second, they ended their workout with ketone supplements.
The finding: Supplementing ketones after the workout led to 20 percent higher EPO levels—the hormone that boosts red blood cell production and oxygen delivery.
So Roche started experimenting. He began taking ketones a few days a week after his workouts, but changed nothing else. He wrote2 of the results:
In October, at the Blue Sky Marathon, I closed the final four miles two minutes faster than last year to set a course record.
That probably had nothing to do with ketones, right? I’m no Olympian, but I train hard. And when looking back on the race and why I could finish so fast while feeling so good, I would be burying my head in the sand not to consider one of the only variables that changed.
Then he set the Leadville record. Afterward he started talking openly3 about his use of ketone supplements on Twitter and on Rich Roll’s podcast4.
Roche is very measured in his claims and is also honest about the downsides. His testosterone levels dropped on his latest blood test—a known side effect of ketone supplementation in healthy males.
Ketones 101
Before we dive deeper, let’s cover ketones. If you’ve listened to any health podcasts or seen a diet book in the last decade, you’ve probably heard of the ketogenic diet or ketones.
Ketones are a fuel your body produces when it breaks down fat for energy, especially when it doesn’t have glucose for fuel. It works like this:
Your body typically runs on glucose from carbs.
When glucose levels run low—through starvation, extreme carb restriction, or prolonged exercise—your body starts breaking down fat for fuel.
Some of that fat gets converted into ketones, an alternative energy source.
This fat-burning, ketone-producing state is called ketosis.
In the 1920s, doctors discovered that forcing the body into ketosis through an extremely low-carb, high-fat diet could treat certain medical conditions, especially epilepsy5.
By the 1970s, the diet gained popularity among weight loss gurus, and it resurged in the late 2010s and early 2020s.
Meanwhile, research was building, suggesting that the ketogenic diet had mental and physical benefits.
The downside is that the diet is impractical. It requires that 80 percent of your food be fat and only 5 percent (or less) be carbs. That’s a lot of oil, butter, and fatty meat and very few vegetables.
Enter the supplement industry.
By 2015, researchers had figured out how to put ketone precursors in a bottle. Brands like KetoneAid, Ketone-IQ, and Pruvit started marketing “exogenous ketones”—ketones you consume rather than produce naturally.
The idea was that supplements could give us the benefits of ketosis without the gross and impractical diet.
Brands claim ketone supplements are “nature’s superfuel” that gives you a “radical boost in focus, endurance, and performance.”
But as with most hyped supplements, the reality is more complicated.
What the Research Really Shows
I wanted to cut through the marketing claims, so I called the guy who literally invented exogenous ketone supplements: Dominic D’Agostino6, Associate Professor at the University of South Florida.
D’Agostino has been researching ketones for over 15 years and has co-authored some of the most-cited papers on the topic7.
“The military initially funded me to develop a strategy to enhance the safety, performance, and resilience of war fighters in extreme environments … NASA was also interested in ketone supplements for the space environment … They were like, ‘Go invent a ketogenic diet in a pill,’” D’Agostino told me.
For performance, D’Agostino has found ketone supplements help, but not by much.
“Humans only get a 1 to 2 percent increase in performance (from ketone supplements),” D’Agostino told me. “Caffeine will give you 2 to 4 percent if you're drinking 400 to 500mg.”
Translation: Your morning coffee probably does more for your workout than expensive ketone shots, all for less money. Ketone supplements cost roughly $4 per serving, while caffeine is readily available for less.
But there is a caveat to ketone supplementation, and it goes back to why the military and NASA funded D’Agostino in the first place. “Performance is enhanced if you put someone in a very extreme environment, like what we study. For example, on top of Mt. Everest or in space,” said D’Agostino.
The most interesting performance benefit isn’t physical—it’s cognitive.
D’Agostino's lab found that ketones help preserve mental function during physical exhaustion. Basically, you make fewer dumb decisions when you’re tired, which can enhance performance outcomes in extreme events and environments.
That might explain why someone like Roche, running 100 miles through Colorado’s mountains, noticed benefits.
Beyond Performance: Where Ketones Actually Shine
D'Agostino got most excited when we moved away from performance and talked about the medical application of ketosis, where the science is much stronger.
Ketone supplements show promise for type-2 diabetes management and certain brain disorders. They are “therapeutically linked to better outcomes for brain disorders, metabolic management of cancer, anti-anxiety effects, and a small but significant improvement in cognitive function,” D’Agostino said.
“What was prominent (in our work) was the anti-anxiety effects,” he said. “We were giving ketones to rats and mice, and realized that they weren’t trying to bite us. They were much more calm.”
Ketones seem to work on the same brain receptors as alcohol and anti-anxiety medications, producing a calming effect. This mechanism also helps explain why ketones are so effective against seizures.
“If you put someone with epilepsy onto a ketogenic diet, roughly two-thirds will have amazing seizure control, and 15 percent will be hyper-responders, meaning they never get seizures again,” D’Agostino told me. “The ketogenic diet actually works better for seizures than all drugs we know of.”
The Supplement Reality Check
When I asked D’Agostino about popular ketone supplements, he noted that, “Many products on the market are liquid ketones, so they're not necessarily ketones, but precursors to ketones.”
In other words, you’re not always getting what you think you’re paying for.
He’s also wary of the health influencers and MLM schemes pushing ketones for weight loss. While animal studies show modest weight reduction, the human evidence is thin.
For performance, D’Agostino did concede that, for extreme conditions or hardcore endurance athletes, there may be some benefit. But those benefits pale in comparison to smart training, sleep, and proper nutrition.
The Takeaways
Here’s where we landed after talking to the leading researcher and reviewing the science:
Ketone supplements might help if you’re:
Running ultra-marathons or competing in extreme endurance events. Take them after training.
Dealing with specific medical conditions (under medical supervision).
Wealthy enough that $3-5 per serving doesn’t matter and want to experiment and see what happens.
They’re probably unnecessary if you’re:
A recreational athlete—i.e., not sponsored or getting paid to exercise.
Trying to lose weight or suppress appetite.
Operating on a normal human budget.
For most Two Percent readers grinding through morning workouts or weekend adventures, ketone supplements are expensive solutions to problems you probably don’t have.
That 1 to 2 percent performance boost is barely outside the margin of error and will cost more than your gym membership.
Your time, money, and mental efforts are likely better spent on dialing in your sleep, exercise, and nutrition—and drinking a good cup of coffee before a workout.
David Roche’s Leadville success is impressive, but he’s also an elite athlete running 100 miles in extreme conditions—precisely the scenario where ketones may help.
Or as D’Agostino diplomatically put it: “For the average person, the benefits are going to be minimal.”
Back to Michael. Thanks to Emily for the informative post!
Have fun, don’t die,
-Michael
Evans, E., Walhin, J.-P., Hengist, A., Betts, J. A., Dearlove, D. J., & Gonzalez, J. T. (2023). Ketone monoester ingestion increases postexercise serum erythropoietin concentrations in healthy men. American Journal of Physiology–Endocrinology and Metabolism, 324(1), E56–E61.
It’s also worth noting that this study was small: Just 9 people.
https://www.trailrunnermag.com/training/trail-tips-training/the-wild-uncertain-science-of-post-exercise-ketones
https://x.com/MountainRoche/status/1835679707200713032
https://www.richroll.com/podcast/david-roche-875/
Sophie Höhn, Blandine Dozières-Puyravel, Stéphane Auvin, History of dietary treatment from Wilder's hypothesis to the first open studies in the 1920s, Epilepsy & Behavior, Volume 101, Part A, 2019, 106588, ISSN 1525-5050.
https://health.usf.edu/medicine/mpp/faculty/ddagosti
https://scholar.google.com/citations?user=3LSCEEYAAAAJ&hl=en&oi=ao
Great analysis and helpful recommendations/ summary. Appreciate the article!
Good deal, one less thing I need to spend money on… :-)
Thanks, very informative post!